Chapter 2 | Oxygenation and the Fundamentals of Mechanical Ventilation


In Chapter 1, we talked about spontaneous breathing as an elegant and effortless process. Comparing spontaneous breathing to mechanical ventilation is like comparing a gentle stream to powerful rapids. During mechanical ventilation, the diaphragm is being bypassed, or in many cases (i.e., sedation, paralysis) knocked out completely. Air is pushed in by generating a high pressure outside the lungs. Mechanical ventilation pushes air into the lungs with a driving force that is generated inside the ventilator and delivered into the lungs through the ventilator circuit and endotracheal tube. We are now dealing with a positive pressure being applied to the lungs instead of the negative pressure that is usually generated with spontaneous breathing via the diaphragm. This driving force (or positive pressure) can be very traumatic to the fragile alveoli in the lungs—imagine wanting to water your garden but instead of a sprinkler, you use a power washer—however, you will begin to learn how to minimize this trauma for the patient, while ensuring effective oxygenation.

In this chapter, you will learn why and when mechanical ventilation is used, and the physiology of a mechanically delivered breath. You will explore supplemental oxygen and its impact on the body. Finally, you will revisit PEEP and FiO2, but this time within the context of mechanical ventilation.


Understanding how mechanical ventilation works will equip you, the health care practitioner, to protect the lung from unwanted damage. You will also learn the basics of selecting appropriate oxygenation for a ventilator patient.

Learning Objectives

At the end of this chapter, you will be able to:

  1. Discuss the concept of mechanical ventilation as a sealed system
  2. Specify healthy oxygen saturation levels and how to titrate supplemental oxygen optimally
  3. Explain how PEEP and oxygen work together to aid in oxygenation
  4. Explain why lung protective strategies are necessary in mechanical ventilation

Key Terms

In this chapter, you will learn about all of the following key terms. These terms will be used throughout this book, so it is important to take the time to master them and practice your recall often.

  • hypoxic failure
  • hypercapnia
  • ineffective drive to breathe
  • lung protective strategies
  • Fraction of Inspired Oxygen (FiO2)
  • room air
  • supplemental oxygen
  • saturation of hemoglobin in the blood (SpO2)
  • hemoglobin
  • oxygen content (CaO2)
  • oxygen free radicals
  • titrate

Whenever these terms are first introduced in this chapter, they are bolded. However, if you need additional information about a term than what is provided here, you can research it in The Free Dictionary: Medical Dictionary.


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